Vibrating screen



'Oct' 1927 B; A. MITCHELL 1,645,613

' VIBRATING SCREEN Filed Jan.23, 1926 2 Sheets-Sheet 1 IN VE N TOR Q ATTOR/VEKS Oct.

1927 B. A. MITCHELL VIBRATING SCREEN Filed Jan.23. 1926 2 Sheets-Sheet 2 A TTOR/VEYJ Patented Oct 18, 1927.

UNITED STATES BENJAMIN A. MITCHELL, F TOMPKINSVILLE, NEW YORK VIBRATING sonnnn.

Application filed January 28, 1926. Serial No. 83,184.

In the practical operation of vibrating screens of the type shown in several Letters Patent of the United States granted to thepresent applicant. June- 26, 1923, Nos.

1,459,841; 1,459,842; 1,459,848; 1,459,844; 1,459,845; 1,459,846, it has been found that the great rapidity of vibration approximating 3500 vibrations per minute, brings about crystallization in the frame which supports "the screen cloth and at the nodes of vibration of the screen cloth itself, which results in breakage of the frame and of the screen cloth after a too short period of use. The

members of the framev which break by reason of such crystallization can be replaced readily and without great expense and the screen cloth itself can be renewed, as it must be at somewhat longer periods by reason of wear, but it has been found desirable to prolong the period of use before breakage results from crystallization and in the effort to meet the situation it has been found that crystallization takes place much more slowly, both in the frame and in the screen cloth itself, if the screen cloth is connected to the vibrator, by which the required vibrations are produced, by connections which possess a limited degree of flexibility or resilience and can best be described as non-rigid, so that the screen clothshall not be held in rigid relation with the vibrator as heretofore. It is found, moreover, that the improved result is attained whether the vibrator is supported from the main frame and itself carries or supports the screen, .or the screen itself is supported from the main,

frame and carries or supports the vibrator.

. In the embodiment of the invention which has been chosen for illustration and description, the vibrator is supported from the main frame and itself carries or supports the screen cloth, but it will be obvious that the alternative arrangement might be adopted.

In the drawings in which the invention is illustrated 1 Figure 1 is a view in side elevation of a com lete screen structure which embodies the invention.

Figure 2 is a top view of the same, partly broken out to save space.

Figure 3 is a detail View in section on the plane indicated by the broken line 3-3 of Figure 1 and on a larger scale.

Figure 4 is a detail view in side elevation of a portion of the structure shown in Figure 3.

Figures 5, 6, and 7 are detail views illustrating features of construction to be referred to, w1 th particular relation to the manner 111 which the screen cloth is carried by the supporting aprons.

v Figure 8 is a detail view illustrating more partlcularly the means by which the side aprons are connected to the vibrator.

In the embodiment of the invention illustrated particularly in Figures 1 and 2, a suitable frame a, preferably constructed of angle iron, has two cross members a and a upon which is supported a saddle piece I). The latter receives in a spherical bearing the cas-. ing 0 of the vibrator. At each'end of the casing is secured by a bar (1 and bolts (1' a spider (Z to which is secured a correspond- 1ng side apron e of sheet metal by which the screen cloth f is supported, the aprons havlng some degree of flexibility or resilience and being non-rigid. In the construction,

shown there are two screen cloths f and f, one above the other, the one screen cloth I being supported by the aprons e and the other screen cloth f being supported by the aprons e, as more particularly described hereinafter. 4

Each apron e and e is formed at its lower edge with a flange e and each screen cloth f has applied along its edge a folded strip f of metal which embr frees the edge of the screen cloth and is secured at intervals by rivets F. The edge of the screen cloth and the reenforcing strip f are bent in U-form, as clearly shown in Figures 3 and 7 to engage the flange e of the corresponding apron e, c. .When the screen cloth and the aprons are thus engaged the two aprons at opposite edges of the screen-cloth are spread apart by spreader rods 9 in the case of the lower screen cloth f. When two or more screen cloths are placed one above another, as in the construction illustrated, the two aprons e which engage the screen cloth f are spread apart by spreader rods g which pull the aprons a respectively toward the aprons e, the latter being already spread by the rods 9. It is important, in order that the non-rigid quality of the supporting connections may be preserved, that the spreader rods 9 and 9 shall not destroy the capacity for relative movement between the opposite rod 9 has a loose fit in the apron e, as indicated at e in Figure 3. Furthermore, the nut 9 threaded on the end of the rod g, outside of the apron e, the nut which forms the head 9 of the rod, and each washer 9 applied to the rod on the inside face of the apron e, and retained by the pinned collar 9', has a convex surface to bear against the apron. Likewise the head g of each rod or bolt and each pinned collar g at the inner face of the apron c has its contacting face convex. This formation of the contacting members and the looseness of fit of the rods in the apron e permit that relative movement of the co-acting members which assures non-rigid connection and such independence'of movement as is suflicient to prevent crystallization. It might be sufiicient to provide for such loose connection between the rod 9 and one of the apronsat one end only of the rod, although the provisions of loose connection at each end of the rod is desirable. Eachrod g may have the nut g which bears against the inner face of the corresponding apron e fitted to the surface of the apron.

r The upper and lower edges of the screen cloth may be stiffened by being folded about a rod h and riveted as at k.

In order that the screen cloth maybe held at the proper inclination without being so connected to themain frame as to be prevented from proper vibration, each apron or the two aprons e and e at each side have connected thereto at a point to one side of the axis of the vibrator a link 2' which is engaged y a hook is sup orted adjustably on the frame member a by nuts k and a cushionk.

It will be understood that various changes in details of construction and arran ement can be made to suit diiferent conditions of use and that, except as pointed out in the accompanying claims, the invention is not restricted to the particular construction shown and described herein.-

I claim as my invention:

1. In a vibrating screen, the combination of a vibrator, a screen cloth, and non-rigid a rons secured to and supported with the vibrator and supporting the screen cloth.

2. In a vibrating screen, the combination of a vibrator, non-rigid aprons secured to and supported with the vibrator, a screen cloth engaged by the aprons, and means to maintain the aprons in engagement with the screen cloth with freedom for limited relative movement between the aprons.

3. In a vibrating screen, the combination of avibrator, non-rigid aprons secured to and supported with the vibrator, a screen cloth engaged by the aprons, and rods loosely engaged with the aprons to maintain them .1n engagement with the screen cloth with freedom for limited relative movement between the aprons.

' 4. In a vibrating screen, the combination of a vibrator, a plurality of resilient aprons, one outside of the other secured to the vibrator at each end thereof and supported therewith, a plurality of screen cloths one above another and separately engaged by the aprons at each side, and means to maintain the aprons in engagement with the screen cloths.

5. In a vibrating screen, the combination of a vibrator,aplurality of pairs of resilient aprons, the aprons of one pair being outside of those of a second pair and secured to the vibrator, one at each end thereof, a screen cloth engaged by the aprons of the outer pair, ro s engaged with the aprons of the outer pair to maintain them in engagement w1th the screen cloth, the second pair of aprons also being secured to the vibrator,v

one at each end thereof, a second screen cloth engaged by the aprons of the second jpair in a different plane from that of the rst cloth, and means to maintain the aprons of the second air in engagement with the second screen c oth.

6. In a vibrating screen, the combination of a vibrator, a plurality of pairs of resilient aprons, the aprons of one pair being outside of those of a second pair and secured to the vibrator, one at each end thereof, a screen cloth en aged by the aprons of the outer pair, ro s engaged with the aprons of the outer pair to maintain them in engagement with the screen cloth, the second pair of aprons also being secured to the vibrator,

one at each end thereof, a second screen cloth enga ed by the aprons of the second pair-in a ifl'erent plane from that of the first. cloth, and rods engaging the aprons of the two' pairs at each side to maintain the aprons of the second pair in engagement with the second screen cloth.

7. In a vibrating screen, the combination of a vibrator, non-rigid aprons secured to and supported with the vibrator and having outturned flanges at their edges, a screen cloth engaged by the flanges of the aprons,

and spreading rods loosely engaging theaprons to maintain them in engagement with the screen cloth while permitting relative movement between theaprons.

This specification signed this 19 day of January, A. D. 1926. I

BENJAMIN A. MITCHELL. 

